Large, heavy objects such as file cabinets and refrigerators must often be moved from one floor to another within a warehouse of office building or the like. Although such objects can easily be moved along a level floor by use of a "dolly" or handtruck, difficulty is experienced in moving objects of this type from one floor to another in the absence of elevators. Such bulky and weighty objects are ordinarily "manhandled" up and down stairs; that is, the objects are physically lifted by a team of workmen and carried up and down stairs. Labor costs are thus high, and the chances of injury are large.
Efforts have been made in the past to provide mechanical carriers for carrying large objects up and down stairs; representative of these carriers are those of U.S. Pat. Nos. 2,928,501 and 3,512,658. These devices are not easily loaded and unloaded, however, and either require the use of a separate "dolly" in conjunction with stair climbing or require a human operator to bear a portion of the weight of the load as the load is moved.